1. Field of the Invention
The present invention relates to a method for monitoring a battery and a battery that is configured to carry out the method.
2. Description of the Related Art
An interconnection of several galvanic cells, which are, as a rule, substantially identical, is referred to as a battery. It constitutes an electrochemical energy store and an energy converter and is provided for supplying electrical energy. When discharging occurs in the battery, stored chemical energy is converted to electrical energy by the electrochemical reaction. The cells of the battery, which may be connected in parallel or in series or a mixture of the two, are arranged in so-called modules. One or more of these modules, connected in series or parallel, form the battery.
In the case of the above-mentioned cells, primary cells, which are not rechargeable, are distinguished from secondary cells, which are rechargeable. A rechargeable battery is also referred to as an accumulator having accumulator cells. In the following, both a non-rechargeable and a rechargeable battery are to be understood as a battery.
In motor vehicles, a so-called starter battery, which is configured, e.g., as a lead-acid battery, is used, on one hand, for providing the electric current for the starting motor of the internal combustion engine. In addition to powering the starting motor, the battery also powers the other electrical load circuits in the vehicle. To start the internal combustion engine, high currents are required for a short period of time, the high currents also having to be provided at low temperatures.
On the other hand, in motor vehicles, in so-called electric vehicles and hybrid vehicles, batteries are used as power sources for propelling the vehicle. These are also referred to as traction batteries.
It is always necessary to monitor the operability of the battery in the vehicle regularly or even continuously, in order to ensure reliable operation of the motor vehicle. To this end, parameters or operating variables of the battery, such as terminal voltage, temperature, pressure, in particular, the internal cell pressure, current, impedance, etc., are recorded.
It must be taken into consideration that in the construction of accumulator modules for hybrid and electric vehicles, up to 100 or more individual cells are interconnected and packed together. In this context, up to now, only the voltage of each cell has been measured. However, further parameters, such as the temperature, are only measured in a small portion of the cells of an accumulator module. Ideally, at least the temperature of each cell should be individually measured during operation. However, this would mean a very high expenditure for wiring.
A battery including battery cells, and a method for monitoring the battery, are known from the printed publication published international patent application document WO 2009/149690 A1. In this context, the battery has a multitude of battery cell stacks connected in series; a battery cell stack being able to include a single battery cell or to be made up of battery cells connected in parallel. Sensors monitor the state of charge of individual battery cells. The battery described is assigned a charge-balancing device (cell balancing), which includes a target value table of the permissible state of charge of individual battery cells. The charge-balancing device varies the charging state as a function of the state of charge. When the target value for the state of charge of individual battery cells is reached, the charge balancing of the battery cells is interrupted. A tap of a charge-balancing lead is situated at each battery cell; the charge-balancing leads being united in a wiring harness and supplied to designated cell-monitoring modules, which have, for their part, sensors and cell-monitoring circuits; these components of the cell monitoring being positioned together in the charge-balancing device, spatially separated from the battery cells.